865 research outputs found
A method for in situ SEM fracture studies of brittle materials using the double torsion technique : application to nuclear graphite
No full textThis work concerned the design and development of a miniature double torsion (DT) testing rig, for use inside the chamber of a scanning electron microscope, to perform in situ loading studies of brittle materials using the DT fracture mechanics specimen. The in situ performance of the system inside the SEM was highly satisfactory, while still providing free rotation of the attached stepper motor. Crack growth rates of down to 19nm/s were directly observed in PMMA specimens. It was concluded that the technique displayed merit in its ability to contribute to the knowledge base of slow cracking and damage development in brittle materials, with the advantage being that the gearing ratios of the current device resulted in slower specimen loading rates, which were more controlled, than reported previously
Microstructural Changes in Clays Generated by Compression Explored by Means of SEM and Image Processing
No full textAbstractA study on the microstructure of an illitic marine clay is carried out through a thorough investigation of the clay origin, composition and current microstructure. The clay fabric is investigated by means of scanning electron microscopy (SEM) and statistically analysed by means of image processing. The nature and strength of the clay bonding are probed by means of direct chemical micro-analyses and on purpose strain paths. The same investigation is carried out both on the natural and on the reconstituted clay, at the initial state and after one-dimensional compression to medium and large pressures
The ITZ in concrete with natural and recycled aggregates: Study of microstructures based on image and SEM analysis
No full textAim of this work was to investigate the microstructure of the Interfacial Transition Zone (ITZ) between cement paste and aggregate in concrete utilizing Scanning Electron Microscope (SEM) in order to identify possible effects on the ITZ related to different recipes and production parameters. SEM is an important tool to carry out concrete, cement and aggregate microstructure characterization. SEM imaging facilitates identification of elements in concrete. Thanks to the higher spatial resolution, and the analytical capabilities, it allows to perform a materials-imaging-related analysis. Many information can thus be extracted from these data, such as composition, phase abundance and distribution. In particular, during the last years, backscattered electron imaging of polished surfaces became an important method for the study of cement and concrete microstructures. The technique has many advantages, as the possibility to visualize representative cross-sections over a wide range of magnifications and to correlate image contrast with materials composition (i.e. atomic number). Comparing the information acquired starting from SEM imaging and X-ray microanalysis, the complex microstructure of concrete can be analyzed and images with sub-micrometer definition acquired and processed, obtaining compositional, morphological and morphometric information allowing to understand and evaluate the mechanism affecting the interaction of the aggregates with the cement paste. A common image representative of the ITZ in concrete involves approximately a domain of about 30 ?m surrounding each aggregate and showing, theoretically, an increase of the porosity at the aggregate interface. In order to study this transition zone, 12 different types of concrete mixtures were analyzed, characterized by different combination of cement and virgin/recycled aggregates. The influence of these aggregates (i.e. virgin and recycled) on the resulting concrete microstructure was studied. The significant morphological and overall textural characteristics (i.e. area with higher porosity around aggregate, micro-cracks, size of the crystals in the ITZ) were detected by SEM analysis. Image analysis and SEM investigation, obtained from different concrete samples, provided very interesting results due to the different porosity and the possible interactions between the aggregates and the cement paste.Structural EngineeringCivil Engineering and Geoscience
Pollenkitt ropes of Notopora schomburgkii Hook. f. (Ericaceae, Vaccinieae)
No full textPollen morphology of Notopora schomburgkii Hook. f. was examined using light (LM), scanning (SEM) and transmission electron microscopy (TEM). Pollenkitt ropes were observed and reported for the first time on pollen grains of N. schomburgkii, Ericaceae. With TEM these ropes show lipidic (“pollenkitt-like”) electron density but also show some resistance to acetolysis
Burn wounds after electrical injury in a bathtub: A case report
No full textBackground: Increased smartphone use among minors makes our population more prone to electrical injury. Despite regulations on electrical home safety standards, smartphones and chargers still pose a risk for severe injury among users. Case presentation: We present a case of a patient with low-voltage electrical burns due to smartphone use in a bathtub. The 13-year-old Caucasian patient was using a smartphone plugged into the electrical grid while taking a bath. We report the burns and their treatment. We discuss the likely burn mechanism. Conclusions: Burn wounds after electrical injury due to smartphone use are rare. The presented case shows the danger of smartphone use in bathtubs
A new modular mechanism that allows full detachability and cleaning of steerable laparoscopic instruments
No full textBackground: Ever since the introduction of laparoscopic surgery, researchers have been trying to add steerability to instruments to allow the surgeon to operate with better reachability and less tissue interaction force. Traditional solutions to introduce this often use a combination of springs, cables, pulleys, and guiding structures, resulting in instruments that cannot be properly cleaned and thus are very costly to manufacture and maintain. The aim of the study is to develop a novel affordable, sustainable, cableless, and fully steerable laparoscopic grasper, and to test its ease of assembly, disassembly, and use. Methods: A set of requirements was defined to ensure that the instrument can be handled efficiently at the sterilization unit and in the operating room. Based on these, a multisteerable, cableless 5 mm laparoscopic instrument that operates based on shaft rotations was developed. To test its assembly and disassembly, ten participants were asked to fully dismantle the instrument and reassemble it a total of 60 times. In addition, ten medical students were asked to use the grasper in the ForceSense box-trainer system on a newly developed 3D pick-and-place task, to determine the control effort based on learning curves of steering errors, task time, instrument path length, and maximum tissue interaction force. Results: All important design requirements were met. The recorded data indicates that ten engineering students were able to fully dismantle and reassemble the instrument shaft in 12 s (SD7) and 65 s (SD43) seconds at the sixth attempt. The learning-curve data indicates that three attempts were needed before the ten medical students started to use all steering functions. At the sixth attempt, on average only 1.25 (SD0.7) steering errors were made. The steepest slope in the learning curves for steering errors, path length, and task time was experienced during the first three attempts. In respect of the interaction force, no learning effect was observed. Conclusion: The multi-DOF (degree of freedom) cableless grasper can be assembled and disassembled for cleaning and sterilization within an acceptable time frame. The handle interface proved to be intuitive enough for novices to conduct a complex 3D pick-and-place task in a training setting
Performing probe experiments in the SEM
No full textA four nanoprobe system has been installed inside a FEI XL30 F scanning electron microscope (SEM), and shown to be fully compatible with the normal functions of the SEM and also a Gatan cold stage (model C1003, -185-400degreesC). With some selected examples of applications, we have shown that this nanoprobe system may be used effectively for gripping, moving and manipulating nanoobjects, e.g. carbon nanotubes, setting up electric contacts for electronic measurements, tailoring the structure of the nanoobject by cutting, etc. and even for making unexpected nanostructures, e.g. a nanohook. Applications in other areas have also been speculated, limitations or disadvantages of the current design of the probe system were discussed, and methods for possible improvement were suggested. (C) 2004 Elsevier Ltd. All rights reserved.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000221721000015&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701MicroscopySCI(E)CPCI-S(ISTP)PubMed3
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
Assessment of technical skills based on learning curve analyses in laparoscopic surgery training
No full textBackground: Objective force- and motion-based assessment is currently lacking in laparoscopic skills curricula. This study aimed to evaluate the added value of parameter-based assessment and feedback during training. Methods: Laparoscopy-naïve surgical residents that took part in a 3-week skills training curriculum were included. A box trainer equipped with the ForceSense system was used for assessment of tissue manipulation- (MaxForce) and instrument-handling skills (Path length and Time). Learning curves were established using linear regression tests. Pre- and post-course comparisons indicated the overall progression and were compared to predefined proficiency levels. A post-course survey was carried out to assess face validity. Results: In total, 4,268 trials, executed by 24 residents, were successfully assessed. Median (interquartile range) MaxForce outcomes improved from 2.7 Newton (interquartile range 1.9–3.8) to 1.8 Newton (interquartile range 1.2–2.4) between pre- and post-course assessment (P ≤ .009). Instrument Path length improved from 7,102.2 mm (interquartile range 5,255.2–9,025.9) to 3,545.3 mm (interquartile range 2,842.9–4,563.2) (P ≤.001). Time to execute the task improved from 159.8 seconds (interquartile range 119.8–219.0) to 60.7 seconds (interquartile range 46.0–79.5) (P ≤ .001). The learning curves revealed during what training phase the proficiency benchmarks were reached for each trainee. In the survey outcomes, trainees indicated that this curriculum should be part of a surgical residency program (mean visual analog scale score of 9.2 ± 0.9 standard deviation). Conclusion: Force-, motion-, and time-parameters can be objectively measured during basic laparoscopic skills curricula and do indicate progression of skills over time. The ForceSense parameters enable curricula to be designed for specific proficiency-based training goals and offer the possibility for objective classification of the levels of expertise
Cuidando do recém-nascido em UTIN: convivendo com a fragilidade do viver/sobreviver à luz da complexidade
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Programa de Pós-Graduação em Enfermagem, Florianópolis, 2009.Este estudo trata da elaboração de um modelo que contempla o fenômeno do cuidado em Unidade de Terapia Intensiva Neonatal a partir da compreensão do ser e fazer enquanto enfermeiro neste sistema complexo. Tal compreensão aborda as transformações ocorridas desde a criação das UTINs até a atualidade, vislumbrando sua busca pela integralidade ao oferecer um cuidado sensível e compartilhado. O referencial metodológico da Teoria Fundamentada nos Dados (Grounded theory) associado ao Paradigma da Complexidade de Edgar Morin foi utilizado na análise e na construção do Modelo Teórico: CUIDANDO DO RECÉM-NASCIDO EM UTIN: Convivendo com a fragilidade do viver/sobreviver à luz da complexidade. Participaram da pesquisa 11 sujeitos, entre enfermeiros e mães com bebês internados na UTIN. Utilizou-se a entrevista aberta para coleta dos dados. A análise comparativa dos dados subsidiou o processo de codificação, amostragem, saturação teórica, ordenação e integração dos dados. Os dados foram inseridos no software NVIVO, dando seqüência na organização e agrupamento dos mesmos. A organização dos códigos foi feita de acordo com suas propriedades e, então, agrupados em códigos preliminares, subcategorias e categorias. Através das inter-relações entre categorias, emergente dos dados coletados, identificou-se a categoria central, eixo norteador do Modelo Teórico, e integradora das categorias analíticas denominada: Convivendo com a fragilidade do viver/sobreviver: cuidado altamente complexo, sensível, singular e compartilhado em torno da qual giram as demais categorias: Buscando conhecimentos e competências; Gerenciando o cuidado na UTIN e Vivenciando as singularidades na UTIN. Neste contexto, o cuidado em UTIN se fortalece como uma das áreas da Enfermagem em constante desenvolvimento, visando conciliar os avanços tecnológicos importantes para o sobreviver do bebê prematuro com abordagens que valorizam as inter-relações em seu quotidiano, de modo sistêmico. Busca atuar nas diversas esferas do cuidado complexo em saúde, desde os serviços de apoio da instituição hospitalar e seus gestores até a academia, visando evitar atuações compartimentadas e isoladas, integrando e aplicando conhecimentos científicos, com ganhos para a prática profissional. Oferecer suporte tecnológico já não basta. A pesquisa ressalta que é necessário exercitar as potencialidades já inatas dos profissionais de enfermagem e caminhar para o encontro de outras, um verdadeiro convite a novas percepções de cuidar do neonato, sua família e os membros deste sistema complexo, numa constante inquietação e adaptação para as demandas que surgem. Assim, as indagações norteadoras desta pesquisa convidam para a ampliação de novos horizontes de investigação, de forma que as possibilidades de estudos indicadas permitam o aprofundamento no âmbito das organizações de saúde e da academia.This study deals with the elaboration of a model which contemplates the phenomenon of care in a Neonatal Intensive Care Unit (NICU), based on the comprehension of the human being and human actor as a nurse in this complex system. Such comprehension encompasses the transformations which have occurred since the creation of the NICUs, discerning its search for the entirety to offer sensible and shared care. The methodological reference of the Grounded Theory associated with Edgar Morins Complexity Theory was utilized in analysis and the construction of the Theoretical Model: CARING FOR THE NEWBORN IN THE NICU: Living with the fragility of living/surviving in the light of complexity. The sample was composed of 11 subjects, including nurses and mothers with newborns in the NICU. Open interviews were used in order to collect data. Comparative data analysis subsidized the data codification, sampling, theoretical saturation, ordering, and integration processes. Data was inserted into NVIVO software, providing a sequence in data organization and grouping. Organizing the codes was done according to their properties and thus, grouped in preliminary codes, subcategories, and categories. Through the relationships in these categories which emerged from the data collected, the central category, the guiding axis of the Theoretical Model and the integrating factor of the analytical categories was identified, denominated: Living with the fragility of living/surviving: highly complex, sensitive, singular, and shared care around which are the following categories: Seeking knowledge and competencies; Managing NICU care; and Living the singularities of the NICU. In this context, NICU care is strengthened as one of the Nursing areas in constant development, seeking to conciliate important technological advances towards premature newborn survival with the approaches which systematically value day-to-day relationships. It seeks to enact in the diverse spheres of complex health care, from the support services of the hospital institution and its management to academia, searching to avoid fragmented and isolated care through integrating and applying scientific knowledge with gains for professional practice. Offering technological support is no longer enough. Research highlights that it is necessary to exercise already innate potential in nursing professionals and work towards finding others, a true invitation towards new perceptions for care for the newborn, his/her family, and the members of this complex system in a constant unrest and adaptation of demands which may arise. Thus, the guiding questions of this study invite towards the amplification of new investigative horizons, in such a manner that the possibilities for suggested studies permit more profound in the realm of health care and academic organizations
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